The invention relates to an electromagnetically actuated directional control valve.
Such an electromagnetically actuated, hydraulic directional control valve is already known from DE-OS 2 109 770, which is designed as a compact 4-directional-3-position-valve, wherein the actual valve elements are integrated into the magnet housing. This 3/4-directional valve operates with a double-lift magnet, whose armature is attached by way of a cross pin to a tappet connected in one piece to a hollow control slide, which is movable in the longitudinal direction. In the center position the control slide is centered by means of a restoring device with two counter-acting springs, which are tied at both sides of the armature to the tappet and are braced at the housing by means of two individual spring plates. Although the double-lift magnet has some advantages, the control slide of this directional valve is centered purely frictionally connected by means of the counter-acting springs of equal strength, so that the center position is not sufficiently fixed because of the lack of a stop. In many cases such frictionally connected centering is insufficient and leads to an unfavorable construction, particularly since the synchronization of the position of the control edges with the magnet actuation also presents difficulties. Furthermore, the directional valve as proposed requires a special type of construction for the control slide with the tappet, so that standard structural elements cannot be used. In case of an exchange of the spring on the inside, the actual valve has to be disassembled.
Furthermore, an electromagnetically actuated hydraulic 4/3-directional valve is known from DE 29 43 714 A1, whose control slide is centered in a center position by two frontally arranged springs constituting a restoring spring system. Two singly acting solenoids, which are attached to the two opposing front faces of the housing, form an electromagnetic actuating device, by means of which the control slide can be deflected into two working positions on both sides of its center position. This directional control valve which requires two solenoids in order to achieve three positions is constructed comparatively long. In addition, it requires two electrical connecting leads and two plugs, because of which it is relatively expensive to construct and the costs are higher then with a double-lift magnet. In some cases the required space is not available for a directional control valve with two solenoids, so that the application possibilities are limited.